Anomalous single-mode lasing induced by nonlinearity and the non-Hermitian skin effect

TL;DR

This paper introduces a novel laser system where increasing pump power transitions the laser from multi-mode to single-mode operation due to nonlinearity and the non-Hermitian skin effect, promising for high-power laser arrays.

Contribution

It demonstrates a new mechanism for achieving robust single-mode lasing at high powers through nonlinear gain saturation and non-Hermitian effects in coupled resonator lattices.

Findings

Single-mode lasing occurs at high pump powers, opposite to typical lasers.

The behavior is robust against disorder and scalable to large systems.

The mechanism involves interplay between nonlinearity and the non-Hermitian skin effect.

Abstract

Single-mode operation is a desirable but elusive property for lasers operating at high pump powers. Typically, single-mode lasing is attainable close to threshold, but increasing the pump power gives rise to multiple lasing peaks due to inter-modal gain competition. We propose a laser with the opposite behavior: multi-mode lasing occurs at low output powers, but pumping beyond a certain value produces a single lasing mode, with all other candidate modes experiencing negative effective gain. This behavior arises in a lattice of coupled optical resonators with non-fine-tuned asymmetric couplings, and is caused by an interaction between nonlinear gain saturation and the non-Hermitian skin effect. The single-mode lasing is observed in both frequency domain and time domain simulations. It is robust against on-site disorder, and scales up to large lattice sizes. This finding might be useful for implementing high-power laser arrays.